I tried the liquid Nyquil for the first time last night. I think I can safely say, whoa. My friend evilbenfranklin calls it "the sniffling, sneezing, coughing, why did I wake up on the kitchen floor medicine." Save for the tolerance that I've built up with Actifed and Nyquil liquigels, that might have happened to me.
I also understand now why everybody complains about the taste so much. That was truly wretched. I wanted to scrape my tongue afterward.